Six categories of anatomical and electrophysiological experiments are proposed on the normal organization, the development of normal organization, and the effects of injury on normal organization and development of the somatosensory system of monkeys. (1) Microelectrode mapping procedure and anatomical tracers will be used to determine further subdivisions of the somatosensory cortex and thalamus, the interconnections of subdivisions, and areal patterns of intrinsic connections. (2) Single unit recordings and, to some extent, multi-unit recordings will be used to determine how separate cortical body representations differ in neuron response types, and high density single unit "mapping" will be used to determine how neuron response types are distributed within a field, and if "modular" grouping of neuron response types occurs. (3) A limited number of experiments will explore the organization and connections of motor and premotor fields using microstimulation mapping procedures, and anatomical tracers. (4) Experiments will start using anatomical tracers and microelectrode mapping to investigate the normal development of the somatosensory system. (5) The effects of peripheral nerve injury, and central nervous system damage on altering the normal organization of the somatosensory system in adult mammals will be studied with microelectrode mapping procedures. (6) Parallel experiments will compare the effects on somatosensory system organization of peripheral nerve injury and central nervous system damage in newborn and young animals with those found in adults.